1. Field of the Invention
The present invention relates to an optical image offset device for compensating for or producing a lateral offset of an image of an observation object with respect to an optical axis in an optical observation device, that is to say for compensating for an offset perpendicular to the optical axis of the optical observation apparatus. The invention furthermore relates to an optical image stabilization device and to an optical observation apparatus.
2. Description of the Related Art
During the observation of observation objects by means of optical observation apparatuses, the observation object must be kept stationary in order to avoid blurring in the images. This applies in particular when electronic imaging is intended to be carried out with the optical observation apparatus. Movements of the observation optics which take place more rapidly than the imaging lead to blurring in the recorded image, which depending on the situation may be highly problematic.
Unintended movements of the observation optics may for example result from hand trembling in the case of hand-held observation and/or recording apparatuses, for which reason a stand is generally used for prolonged exposure times. Nevertheless, vibrations in mechanical holding devices of an optical observation apparatus can also lead to blurring in the image. In various types of operation, for example, operation microscopes are used which are suspended from a stand.
As a mechanical structure, however, the stand is not infinitely rigid and therefore exhibits a certain degree of deformation under loading. Making the stand infinitely rigid is not technically possible. Furthermore, a high rigidity also entails a very high intrinsic weight. The finite rigidity, however, makes the stand a vibratable system. In other words, the stand may be excited in vibrations owing to impacts or a small periodic external force. If the stand vibrates, then the image quality of the operation microscope is significantly influenced, which entails disadvantages particularly in operations. It has therefore been proposed to equip stands for operation microscopes with vibration damping systems. These typically comprise elements which can exert a force on an element of the stand, so as to counteract stand vibrations. An example of such a stand is described in US 2009/002066 A1.
Furthermore, optical image stabilization systems are known in which lateral movements or tilts of the observation optics relative to an observation object to be observed or recorded are compensated for by displacing a lens or lens group in a direction perpendicular to the optical axis. Optical observation apparatuses having such image stabilization systems are described, for example in U.S. Pat. Nos. 5,270,857 and 5,477,297. Lateral displacement of lenses or lens groups, however, i.e. displacement perpendicular to the optical axis, leads to a reduction in the image quality since all types of non-axisymmetric imaging errors (monochromatic and polychromatic) occur in the optics. The reduction of the image quality therefore needs to be compensated for by additional lenses. In comparison with non-stabilized optics, therefore, stabilized optics have four to five additional lenses but still do not achieve the imaging quality of non-stabilized optics. Furthermore, the lateral adjustment range of the displaceable lenses is relatively small, so that the possibilities of compensating for a lateral image offset are generally restricted to compensating for a small lateral image offset. Systems comprising displaceable lenses are therefore more suitable for compensating for vibrations with small amplitudes.
From U.S. Pat. Nos. 4,881,800 and 6,653,611, image stabilization systems are known which comprise mirrors mounted in such a way that they can be moved about one or two axes, with corresponding drive actuators, by which image displacements perpendicular to the optical axis and tilts can be compensated for.
Besides this, there are image stabilization systems which optically compensate for movements perpendicular to the optical axis by variable prisms or variable wedge-shaped elements, instead of by displaceable lenses. Examples of such systems are known from U.S. Pat. Nos. 5,140,462, 5,280,387, 3,475,074 and 3,942,862.
In U.S. Pat. No. 3,942,862, for example, a variably adjustable optical wedge is described which is formed by two lenses, each having a plane face and a spherical face, the spherical faces of one lens being formed convexly and the spherical face of the other lens being formed concavely. One of the two lenses is mounted in such a way that it can be mechanically rotated about a point lying at the center of curvature of the spherical face. Such an optical wedge, however, has a strongly wavelength-dependent deviating effect, so that it even generates a transverse chromatic error on the optical axis of the optical system. The transverse chromatic error, also referred to as chromatic difference of magnification, leads to color fringing, i.e. colored lines along the edges of an object, since the observation object is magnified with different strengths in different wavelength ranges.
From U.S. Pat. No. 5,280,387, a system is known comprising two identical prisms which consist of the same types of glass and are arranged successively along the optical axis, the prisms being rotatable about the optical axis. An image offset which results from tilting of the optics relative to the observation object can be compensated for by rotating the two prisms about the optical axis. Each of the two identical prisms is composed of two elements consisting of different glass material, the two prisms being oriented relative to one another in such a way that elements consisting of the same glass material lie next to one another. In this way, chromatic aberrations can be kept small.
In relation to the prior art, it is an object of the present invention to provide an advantageous optical image offset device for compensating for or producing a lateral image offset in an optical observation device. It is another object of the present invention to provide an advantageous optical image stabilization device. It is yet another object to provide an advantageous optical observation apparatus. In this context, a lateral image offset is intended to refer to an image offset which is attributable either to an offset of the optical observation apparatus, or its observation optics, perpendicular to the optical axis or to a tilt of the optical observation apparatus, or its observation optics.
The first object is achieved by an optical image offset device according to claim 1, the second object is achieved by an optical image stabilization device according to claim 13, and the third object is achieved by an optical observation apparatus according to claim 16. The dependent claims contain advantageous configurations of the invention.